Eta-phase structures, such as eta-phase carbides, nitrides and carbonitrides are known in the art for use as hardening dispersions in a metal or alloy matrix. Eta-phase materials are conventionally produced by heating metals with a source of carbon or nitrogen. This may be achieved, for example, by vacuum arc melting. Eta-phases can be present in steels containing, for example, nickel and molybdenum and may be formed in situ during thermal processing of these steels. These eta-phases may be crushed and milled to a desired particle size distribution. Typically, this thermal processing involves heating in the presence of sulfur or sulfur bearing compounds. For example, U.S. Pat. No. 4,595,672, Ho et al, teaches a method of producing self-promoted molybdenum sulfide and tungsten sulfide hydrotreating catalysts. The method involves heating one or more molybdate and/or tungstate catalyst precursors of the general formula ML(Mo.sub.y W.sub.1-y O.sub.4), where M is one or more divalent promoter metals selected from Mn, Fe, Co, Ni, Cu, Zn, and mixtures thereof and L is one or more, neutral, nitrogen-containing ligands, at least one or more of which is a chelating ligand polydentate ligand. The heating is conducted in a non-oxidizing atmosphere and in the presence of sulfur or sulfur bearing compounds, such as H.sub.2 S. Sulfur reacts with these catalyst precursors to form sulfided materials.
P. Ettmayer and R. Suchentrunk, "Thermal Stability of n-Carbides", Monatsh. Chem., Vol. 101(4), p. 1098-1103 (1970) also printed in Chem. Abstracts, Equilibriums and Solutions, Vol. 73, p. 313, reference article 92208g, 1970 Edition, disclose the formation of eta-phase carbides having the general formula n-M.sub.56 M.sup.1.sub.6 C where M is Fe, Co or Ni and where Ml is Mo or W. Eta-phase carbides covered in this article include: Fe.sub.6 W.sub.6 C, Co.sub.6 Mo.sub.6 C, Co.sub.6 W.sub.6 C, Ni.sub.6 Mo.sub.6 C and Ni.sub.6 W.sub.6 C. However, the stoichiometry of these eta-phase carbides employ a single carbon atom and only a single metal from groups M and M.sup.1. Moreover, the formation of Fe.sub.6 Mo.sub.6 C eta-phase carbides was not observed.
Conventional eta-phase structures have low surface area and are difficult to synthesize. Therefore, they have not been known or considered for use as catalysts. Also, conventional methods for making eta-phase structures do not produce high surface area eta-phase materials and are not formulated in a nonoxidizing atmosphere free of sulfur or sulfur bearing compounds.
It is accordingly a primary object of the present invention to provide an eta-phase structure in powder form and a method for using the same as a catalyst in converting or producing hydrocarbons in a more efficient manner, particularly from the cost standpoint, than catalysts conventionally used for this purpose.
A more specific object of the invention is to provide a method for producing a high surface area eta-phase powder for use as a catalyst wherein a precursor salt compound is thermally decomposed in a non-oxidizing atmosphere free of sulfur or sulfur bearing compounds to react with carbon, nitrogen or combinations thereof, at an elevated temperature and pressure.
Another object of the invention is to provide eta-phase powder for use as a catalyst effective for hydrocarbon or alcohol production or conversion that provides results similar to those achieved with more expensive noble metals, such as platinum and palladium, conventionally used for this purpose.
Additional objects and advantages of this invention are set forth in the description and examples that follow. Other objectives falling within the scope of the invention will be obvious from the description or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by the compositions and methods particularly set forth herein.